Explosion-proof circuit interrupter



Nov. 2, 1943. o.- SNEUMANN EXPLOS ION-PROOF CIRCUIT INTERRUPTER Filed Dec. 19, 1939 2 Sheets-Sheet 1 F Z Z I F 1 4 Q9 ,45 v

@a a: g 3-5 as WITNESSES: INVENTOR 343 MM 0550 Wen/27742722 2 Sheets-Sheet 2 9 7 a k 5 5 xwxw o. NEUMANN Filed Dec. 19, 1939 EXPLOSION-PROOF CIRCUIT INTERRUPTER Nov. 2, 1943.

INVENTOR 0550 Wed/27742722 BY 4 ATTORNEY 7 WITNESSES: 0 2 741% Patented Nov. 2, 1943 r EXPLOSION -PROOF CIRCUIT INTTERRUPTER .2 l :Otto Neumann, Berlin-Siemensstadt, Germany, assignor to Westinghouse Electric & Manufac turing Company, East Pittsburgh-,;Pa., a corporation of Pennsylvania Application December 19, 1939, Serial No. 310,013 h i 1 In Germany Januaryll), 1939 lfi claims. (o1. 2120-46) I The invention; relates to housed electrical apparatus and more particularly to explosion-proof housings for electrical circuit interrupting de-' vices, such as fuses, switches, circ'uitbreakers, and the like.

For applications of enclosed circuit interrupting devices in mines" and other locations where combustible gases, such as methane, are encountered, it is necessary to maintain a close fit between the abutting surfacesor flanges of the cover and casing-of thedevice, so that combustion penetration of the gas through theair split or gap between the cover and casing flanges can not take place. By combustion penetration is meant the passage of flame and/0r hot gases resulting from an explosion within the housing through the joint between the flanges which are at high enough temperatures to cause ignition of the gas outside of the housing. The width of the flange and the closeness-of the fit must be r such that the gases which pass through the joint are cooled below ignition temperature. 'Hence both the width of flange and the tightness of fit are controlling factors in preventing ignition of the outside gas.

By reason of present developments, for example, in chemical industries'such as in the derivation of artificial rubber,- it is necessary to take other gases into consideration, particularly hydrogen or acetylene. These gases have a considerably greater combustion penetration speed than methane, i. e., they can more readily and rapidly pass through small joints and slits than methane or other heavier gases. Thus, for example, the ratio of the combustion penetration speeds for methane and hydrogen is 1 to 5. For this reason it becomes necessary, in housings for use in such operations, to maintain the air split or gap between the cover and casing flanges as small as possible. For methane, an air gap of not more than .5 millimeter at 25 millimeters flange width is permissible, whereas for hydrogen, the air gap must be not more than .2 millimeter at a flange width of 25 millimeters.

The explosion pressure of almost all explosive gases amounts to approximately seven times atmospheric pressure. This high pressure, which occurs within the housing upon interruption of the circuit, causes an appreciable deformation at the weakest parts, generally at the cover along the spaces between the fastenings of the cover to the casing. The deformation at these relatively weak parts thereby increases the airgap between the flanges-of the ,cover and-casing-at these parts. Whilein the constructions used in locations-where methane is-encountered an increase of thegap up to .5 millimeter is permissible without dangen-a combustion penetration of the gas would take place in the presence of I hydrogen, acetylene or other gases which have a high penetration speed.

An object of the invention is the provisionof an improved explosion-proof housing having a jointbetween the cover and casing which prevents-combustion penetration of gases having high penetrating speeds.

Another object of the invention isthe provision of an explosion-proof cirouit interrupter housing in which the air'split-or gap between the casing and cover is maintained small enough to prevent combustion penetration of gases, and is not increased beyond permissible limits even upon deformation of'the'relatively weak parts of the housing duringan explosion within the housing. I a a Another object of the invention is theprovision of an explosion-proof circuit interrupter housing havingmeans providing a tight joint between the casing and cover which prevents combustion penetration of gases having high penetrating speedseven upon deformation of the cover or casing during an explosion within the housing. I I

Another object of the invention is the provision of an improved explosion-proof housing that is simple and-inexpensive to manufacture.

The objects of the invention are accomplished without the use of asbestos, rubber or textile gaskets, which have not been found to be satishousing and the prevention of combustion penetration were determinative of the number of fastening screws or bolts required for securing the cover on the casing. To control combustion penetration successfully, a substantially largernumber of fastening screws are necessary than to resist explosion pressure alone. The opening or closing of the cover when a large number of fastening screws are used is inconvenient, however. With the construction of the present invention, the number of fastening screws used corresponds only to the number required for controlling the explosion pressure within the housing, while any deformations of the flanges are compensated for by the spring-pressed packing strips, which prevent combustion penetration at the deformed portions.

The novel features that are considered. characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to structure ahd operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of several embodiments thereof when read in conjunction with the accompanying drawings, in which:

Figure 1 is a plan view of an explosion-proof circuit interrupter housing constructed in accordance with the invention; 7

Fig.2 is averticalsectiontl view of the hous ing taken substantially along the line lit-II of Fi Fig. 3 is a transverse sectional view of a 'modification of the invention; I g M Fig. 4 is asectional view of the structiu e shown in Fig. 3, taken along the line IV IV of Fig. 3;

Fig. 5 is a plan view of a modified housing construction; I I p Fig. 6 is a vertical sectional view of the housing shown in Fig. 5, taken substantially along the line VI-VI of Fig. 5; and

Fig. 7 is a fragmentary transverse sectional View of a further modified construction of packing means.

Referring to Figs. 1 and? of the drawings, the I circuit interrupting unit 9 is mounted within an explosion-proof housing ll comprising-a rectangular casing 13 and coperating cover 15, both of which are preferably constructed of cast metal, such as iron, steel or aluminum The; cover 15 is provided with a solid flange ll formed integral therewith and extending entirely around the cover. The flange Hha-s a smooth surface It! which is adapted to abut the smooth finished outer surface of a cooperating flange 23 of the casing l3. The flange -23 is formed integral Withthe casing 43 and is directed inwardly from the walls of the casing.

The cover I5 is secured with its flange IT in tight engagement on the flange 23 of the casing 13 by means of a plurality of screws 25, which extend through openings in the flange l1 and thread into openings the casing flange 23 along the opposite longer sides of the housing. The screws 25 predominantly serve to take up the explosion pressure which arises within the housing H upon interruption of the circuit, and they are preferably spaced closely enough to each other so that on an explosion within the housing practically no substantial deformation of the casing and cover takes place along the portions of the joint at the sides of the housing between the individual fastening screws 2-5., and thus the small air gap along these portions of the joint. at the sides of the housing is not increased beyond safe limits, The sdrews 2-5 are preferably provided with rounded heads havingtriangular for other special shaped depressions therein to prevent unauthorized opening of the cover.

.The portions of the. jointbetween the casing and cover along the opposite ends of the housing are not completely combustion-penetrationproof without the use of some additional means for this purpose, since deformation of the cover or casing at these ends causes an increase in the air gap between the flanges. In accordance with the embodiment of the invention shown in Figs. 1 and 2', the joint is made completely combustion-penetration-proof without the use of a plurality of additional fastening screws along the ends of the housing, by providing packing means indicated generally at 21 between the flanges ii and 2'3 along the ends of the housing.

The packing means for each end of the housing comprises a packing bar or strip 29 of fireproof gas re'sistant material, preferably metal, which is mounted for limited inward and outward movement in a close fitting slot 31 provided therefor in the flange ll of the cover, the slot extending transversely across the entire width of the cover. The packing bar 29 is mounted for limited inward and outward movement-in the slot 3|, by means of a pair of screws 33' which extend through openings provided therefor in the packing bar 29 and thread into the material of the cover at the back of the slots 34. The heads of the screws 33 serve to limit outward movement of the packing bar 29 in the slot 3i, and serve to retain the bar in mounted position when the cover [5 is removed. The

packing bar is resiliently pressed into engagement with the abutting flange 23 of the casing H by means of a plurality of helical compression springs which are disposed between the back of the packingbar 28 and the back of the slot 34.

A plurality of springs ar provided for each l structed to have a U-shaped or H-shaped crosssection to accommodate the heads of the screws 33 and/or the compression springs 35.

The packing bars 2-1! prevent combustion penetration of gases through the .joint along the op posi-te ends of th housing at all times, even during deformation of the cover or casing along the ends of the housing. This results from the fact that the springs '35 maintain the bars in contact with the surface of the casing flange 23 despite deformation of the cover or casing.

In the modification of the invention shown in Figs. -3 and 4-, each of the packing bars 46 has a .T shaped cross-section, and is mounted for limited inward and outward movement in a T-shaped slot 4| provided in the flange I! of the cover. The head of. the slot 4| is of greater depth than the thickness of the head of the packing :bar 4-0 so as to provide for limited inwardand outward movement of the -bar in the slot. Each packing bar 40 is pressed into en'- gagement with the abutting surface of the casing flange -23 by means of a bowed or curved leaf spring 43, which is disposed in the space between the back of the packing bar 4!] and the back of the slot M. The packing bars- M! and slots M in the flange H extend clearacrossthe opposite ends of the housing, and the biasing springs 43 are adapted to be mounted in position in back-of the packing bars 48 by sliding these into the slots through the open end thereof. The biasing springs 43 instead of having a bowed shape may be constructed to have a sinuous orwavy shape, if desired.

The packing means ofthis embodiment of the bustion penetration of gases through the joint between the casing and cover.

Another embodiment of the invention is shown in Figs. and 6. In this embodiment, the packing means mounted in the flange of the cover extends completely around the entire housing. The packing means comprises an endlessmetal packing bar :5 of rectangular outline which is mounted for limited inward and outward movement in a slot 4'! provided therefor in the flange H of the cover l5, the slot-41 extending around the entire length of the flange H. The packing bar 155 is mounted for limited inward and outward movement in the slot 41 by means of a plurality of screws 33, which extend through openings provided in the packing bar and threadinto the materialof the flange H at the back of the slot 47. in countersunk recesses provided therefor in the packing bar 45, and serve to limit outward movement of the bar in its slot.

The packing bar 45 is resiliently pressed into engagement with the casing flange 23 when the cover I5 is in mounted position by means of a plurality of helical compression springs disposed between the back of the packing bar and the back of the slot 41. The compression springs 35 are uniformly distributed along the length of the banand certain of these springs are conveniently mounted upon the screws 33, and others upon the fastening screws 25, which rigidly secure the cover I 5 in mounted position on the casing l3.

Only a relatively small number of fastening screws 25 for fastening the cover to the casing are required with this construction of packing means, since the fastening screws mainly serve to take up explosion pressure within the housing. Thepacking bar 45 prevents combustion penetration of gases/through the joint between the casing and cover at all points around the entire housing. The packing bar accomplishes this function despite deformation of the cover, since the springs 35 maintain the bar in contact with the casing flange 23, even though the cover is deformed along the space between the fastening screws. A fastening screw 25 is provided at each of the four corners of the housing, and also at a point intermediate the corner screws on the-opposite longer sides of the housing. The screws 25 extend through openings provided in the cover :5 and also through openings provided in the packing bar 45. The inner ends of the screws thread into openingsin the flange 23 of the casing l3.

A further modification of the inv/ention is shown in Fig. 7. In this modification the metal packing bar 49 is mounted for limited inward and outward movement in a slot 3| provided therefor in the cover flange I1. The packing bar 49 is mounted for limited inward and outward movescrews 33, and is pressed into engagement with The heads of the screws 33 are disposed the flange 23 of the casing l3 by means of a pm rality of helical compression springs 35 in the same manner as the packing bars disclosed in Figs. 1 and 5. In this embodiment, however, the flange 23 of the casing I3 is provided with a slot 5| into which the packing bar 49 is adapted to be pressed by the springs 35. This construction provides a tortuous path which prevents combus tion penetration of gases through the joint between the casing and cover. The packing bar 49 is maintained in engagement in the slot 5| of the.

casing flange'ZS despite deformation of the cover so as to prevent combustionpenetration of gases through the joint between thecover and casing, the same as in the constructions previously described. The construction shown in Fig. '7 may be applied to two opposite sides of thehousing as shown in Fig. l or the bar 49 may consist of a single continuous bar extending completely around the housing as in Fig.5.

Although the packing bars have been shown in each of the embodiments as mounted in a slot provided in the cover flange, it is to be understood that the packing bars may be mounted'in slots provided in the casing flange and pressed into engagement with the cover flange, if desired. Also, in accordance with another aspect of the invention, the metal packing bars may be disposed in the spaces between adjacent fastening screws. r

The invention is equally applicable to cylindrical housings having rotatable cover which are provided with bayonet-type looks or other fastening means for securing the cover on the housing. In this case, the packing bar would consist of a ring-shaped bar mounted in an annular slot provided in the abutting surface of the housing or cover and pressed by spring means into engagement with the opposite abutting surface.

While the invention has been disclosed in accordance with the provisions of the patent statutes, it is to be understoodthat various" changes in the structural details thereof maybe made without departing from the spirit of the invention. It is desired, therefore, that the language of the appended claims begiven the broadest reasonable interpretation permitted in the light of the prior art.

I claim as my invention: I

1. An explosion-proof circuit interrupter comprising a metal casing and cover having abutting edge surfaces of a width sufficient to provide an explosion-proof joint between the casing and 7 cover, means securing said cover on said casing,

packing means comprising one or more metal packing strips mounted in a recess provided in the edge surface of said cover andbiased by spring means into direct engagement with the metal abutting edge surface of saidcasing' for preventing combustion penetration of gases through the joint between said abutting surfacesij prising a metal casing and cover having abutting flanges provided with abutting surfaces of a width sufiicient toprovide an explosion-proof joint between the casing and cover, fastening means for tightly securing said cover flange to the flange of said casing at a plurality of spaced points, metal packing strips mounted in recesses provided in one of said flanges and resiliently pressed directly in contact with the metal abutting surface of the opposed abutting flange, said strips extending between at least certain of said fastening points.

4. An explosion-proof circuit interrupter comprising a metal casing and cover having abutting flanges provided with abutting surfaces of a width suflicient to provide an explosion-proof joint between the casing and cover, fastening means for tightly securing said cover flange to the flange of said casing at a plurality of spaced points, metal packing strips mounted in recesses provided in one of said flanges and resiliently pressed into direct contact with the metal abutting surface of the opposed abutting flange, said strips extending between at least certain of said fastening points for preventing combustion penetration of gases at the joints between said fastening points and thus eliminating the necessity of providing additional fastening means for this purpose.

5. An explosion-proof circuit interrupter housing comprising a generally rectangular metal casing and cover having abutting surfaces of a width sufl'icient to provide an explosion-proof joint between the casing and cover, a plurality of spaced fastening means for tightly securing the cover to the casing along two opposite sides of the housing, metal packing bars mounted in recesses provided in the abutting surface of said cover along the other two opposite sides of the housing and spring means for biasing said metal packing bars into direct engagement with metal abutting surface of the casing for preventing combustion penetration of gases through the joint between the casing and cover.

6. An explosion-proof circuit interrupter housing comprising a metal casing and cover having abutting flanges provided with abutting surfaces of a width suflicient to provide an explosionproof joint between the casing and cover, means securing said coverin tight engagement on said casing, packing means comprising metal'packing bars mounted countersunk in, the abutting surface of at least one of said flanges between the casing and cover and spring pressed into direct contact with the metal abutting surface of the opposed flange so as to maintain contact with the opposed flange despite deformation. of the cover. v

'7. An explosion-proof circuit interrupter housing comprising a metal casing. and coverhaving abutting flanges provided with cooperating surfaces of a width suflicient to provide an explosion-proof joint between the casing and cover, fastening means securing said cover in tight engagement on said casing, packing meanscomprising metal bars mounted in slots provided in the flange of said cover, between the cover and casing, and spring means for pressing said bars in contact with the cooperating surfac of the opposed flange of said casing so that said bars maintain contact with the opposed flange despite deformation of said cover and prevent combustion penetration of gases through the joint between the casing and cover.

8. An explosion-proof circuit interrupter housing comprising a metal casing and cover having of a width sufficient to provide an explosionproof joint between the casing and cover, fastening means securing said cover in tight engagement on said .casing, packing means comprising one or more metal bars countersunk in part in at least one of said flanges between the casing and cover and springv pressed in direct contact with the metal surface of the opposed flange so as to maintain close contact with the opposed flange despite deformation of the cover to prevent combustion penetration of gases through the joint between the casing and cover.

9. An explosion-proof circuit interrupter housing comprising a metal casing and cover having abutting flanges provided with abutting surfaces of a width sufficient to provide an explosionproof joint between the casing and cover, means securing said cover in tight engagement on said casing, packing means comprising one or more metal packing bars mounted partly countersunk in the abutting surface of at least one of said flanges, spring means for pressing said bars into direct contact with themetal surface of the opposed flange to maintain said bars in close contact with the opposed flange despite deformation of the cover, and means for limiting movement of the bars by said spring means to retain them in mounted position.

10. An explosion-proof circuit interrupter housing comprising a metal casing and cover having abutting flanges provided with abutting surfaces of a width sufficient to provide an explosion-proof joint between the casing and cover, means securing the cover in tight engagement on the casing, packing means comprising one or more metal packing bars mounted in slots provided in one of said flanges between the casing and cover, and spring means for pressing said bars in direct contact with the metal abutting surface ofthe opposed abutting flange for maintaining the bars in contact with the opposed flange despite deformation of the cover, said bars and said slots having a construction which limits outward movement of the bars relative to the slots so as to retain said bars in mounted position when the cover is removed.

11. An explosion-proof circuit interrupter housing comprising a metal casing and cover having abutting flanges provided with abutting surfaces of a width suflicient to provide an explosionproof joint between the casing and cover, means securing said cover in tight engagement on said casing, packing means comprising one or more metal packing bars mounted in slots provided in one of said flanges for limited inward and outward movement in the slots by a plurality of screws, and spring means for pressing said bars in direct contact with the abutting metal surface of the opposed abutting flange to maintain said bars in contact with the opposed flange despite deformation of the housing.

12. An explosion-proof circuit interrupter housing comprising a metal casing and cover having abutting flanges provided with cooperating surfaces of a width suflicient to provide an explosion-proof joint between the casing and cover, a plurality of fastening screws for tightly securing the cover flang to the flange of said casing at a plurality of spaced points, packing means comprising. one or more metal packing bars mounted in slots provided therefor in the flange of said cover, a plurality of helical compression springs for pressing said. bars in direct contact with the cooperating metal surface of the opposed flange of said casing tomaintain said bars in contact with the casing flange despite deformation of said cover, at least some of said fastening screws extending through openings provided in said bars, and at least some of said springs being mounted on said last mentioned fastening screws and disposed between the back of said bars and the back of said slots.

13. An explosion-proof circuit interrupter housing comprising a metal casing and cover having abutting flanges provided with flat abutting surfaces of a width suflicient to provide an explosion-proof joint between the casing and cover, fastening means securing said cover in tight engagement on said casing, packing means comprising a plurality of metal packing bars mounted for limited inward and outward movement in slots provided therefor in one of said flanges, and a plurality of uniformly distributed helical compression springs for each bar for pressing said bars in direct contact with the cooperating metal surface of the opposed abutting flange to maintain said bars in close contact with the opposed flange despite deformation of said housing.

14. An explosion-proof circuit interrupter housing comprising a casing and cover having abutting flanges provided with cooperating surfaces of a width sufficient to provide an explosionproof joint between the casing and cover, fastening means securing said cover in tight engagement on said casing, packing means comprising one or more metal packing bars mounted for limited inward and outward movement in slots provided in one of said flanges, and a curved leaf spring disposed between the back of each bar and the back of its slot for pressing said bars in direct contact with the cooperating metal surface of the opposed abutting flange to maintain said bars in contact with the opposed flange despite deformation of the cover.

15. An explosion-proof circuit interrupter housing comprising a metal casing and cover having abutting flanges provided with cooperating surfaces of a width sufficient to provide an explosion-proof joint between the casing and cover, means for securing said cover in tight engagement on said casing, packing means comprising a metal packing bar mounted for limited inward and outward movement in a slot provided therefor in one of said flanges, said bar extending along said flange substantially completely around the housing, and spring means between the back of said bar and the back of said slot for pressin said bar in direct contact with the cooperating surface of the opposed abutting flange to maintain said bar in close contact with the opposed flange despite deformation of said cover, said packing means preventing combustion penetration of gases through the joint between said casing and cover.

16. An explosion-proof circuit interrupter housing comprising a metal casing and cover having abutting flanges provided with cooperating surfaces of a width sufficient to provide an explosion-proof joint between the casing and cover, means securing said cover in tight engagement on said casing, packing means comprising one or more metal packing bars mounted for limited inward and outward movement in slots provided therefor in the cooperating surface of the flange of said cover and adapted to engage in cooperating slots provided in the surface of the flange of said casing, and spring means for pressing said bars into engagement with the slots of the casing flange, said' packing means preventing combustion penetration of gases through the joint between the casing and cover despite deformation of the housing.

OTTO NEUMANN. 

